Cereal-based foods may be manufactured by a variety of processes.
One category of cereal-based food is wafer. The main types of wafer are described by K. F. Tiefenbacher in “Encyclopaedia of Food Science, Food Technology and Nutrition p 417-420-Academic Press Ltd London—1993”. Wafers can be baked as flat sheets between hot plates as described in GB2221603, or can be baked using shaped moulds into other shapes such as cups or ice cream cones (GB200432). Traditionally, such wafers are made by baking a batter comprising wheat flour, water, some fat, and a raising agent e.g. sodium bicarbonate.
Wafers with a composition that causes them to be flexible when hot can be shaped after baking, for example in the production of rolled wafer cones from a sugar-containing batter. Cereal compositions can also be extruded into narrow strips which are then formed into shapes such as cones (EP 1 323 347 A1).
Flat wafer sheets are used in a number of popular confectionery products such as KIT KAT. Typically the flat wafer sheets may have a fat cream layer applied to them and then several creamed sheets, together with a non-creamed top sheet, and are assembled to form a so-called “wafer book”. The wafer books are cut into small biscuits which can be enrobed or moulded with chocolate.
Extrusion-cooking of cereal-based compositions is commonly used in the food industry. It is described for the preparation of edible food product cups in U.S. Pat. No. 5,962,055, in the making of multiple, complexly patterned extrudates in U.S. Pat. No. 6,251,452 B1, in the manufacture of confectionery having coloured fine line (U.S. Pat. No. 6,579,555 B1), and also in the manufacture of expanded shaped pellets in U.S. Pat. No. 6,586,031 B1. U.S. Pat. No. 6,054,166 further describes a process for making cooked snack by extrusion having a texture similar to traditional tortillas, crisps, or crackers. US 2003/0091698 A1 describes a dough of high-protein food material composition which may be extruded into shape and then baked to form food products such as wafers, flat breads, and waffles. Bread slices or toasts produced by a baking-extrusion-expansion process are described in U.S. Pat. No. 4,217,083.
Dough compositions for making farinaceous snacks are disclosed in WO 99/51111 and WO 02/07538 A2 for instance. DE 31 28 109 A1 also discloses a method for making homogeneous dough strips by extrusion.
The common features of the extrusion processes include the step of forming an extrudable dough, which may be cooked in a single or a twin-screw extruder under high temperature, and which is then extruded through a die. Extrusion through a die may be accompanied by expansion, depending on the water content of the dough and depending on the pressure at the die. The product may then be cut and/or further processed and cooled.
The resulting products manufactured by the extrusion processes described above commonly have disadvantages such as inhomogeneous distribution of the obtained cereal-based product. These problems mean that it has not been possible to use extrusion to produce a uniform large flat wafer sheet, such as would be suitable for feeding a layering process for the production of wafer books.
It is thus an object of the invention to provide a process and a production line which overcome these disadvantages and further improve the efficiency of cereal-based flat wafer production.